This invention relates to dry sodium aluminum hydride and a process for its manufacture
Sodium aluminum hydride, NaAlH.sub.4, is a powerful reducing agent and as such has numerous applications in the chemical and pharmaceutical industries.
Commercially, sodium aluminum hydride, hereinafter SAH, is produced by "direct synthesis", that is, in accordance with the following reaction, EQU Na+Al+2H.sub.2 .fwdarw. NaAlH.sub.4.
The reaction occurs at elevated temperature and pressure, e.g. 285.degree. F. and 2000 psig, and in the presence of a rate promoting amount of titanium which is introduced to the reaction mass along with the aluminum. A catalyst, NaAlH.sub.2 (C.sub.2 H.sub.5).sub.2, is also used. This catalyst can be produced in situ by the reaction of triethyl aluminum with the sodium, aluminum and hydrogen which are already in the reaction mass. The reaction takes place in a toluene reaction medium which forms a slurry with the SAH solid product. This slurry will also contain some aluminum, catalyst and by-product sodium aluminum hexahydride, Na.sub.3 AlH.sub.6. While the SAH product can be kept in the slurry for storage and shipping purposes it must be realized that the slurry is not stable in air and will react violently if it comes in contact with any moisture. Furthermore, the slurry is subject to settling-out, is not always the easiest medium to pump and, because of its liquid component, requires a large storage volume.
As an alternative, the SAH can be stored, shipped etc, in solution with a solvent, such as dimethoxy ethane. This technique answers some of the objections associated with a slurry, but still will require a large storage volume. Also, the use of such ether solvents presents a safety hazard as SAH forms an explosive mixture with ether solvents at relatively low temperatures.
Therefore, there is a need for an SAH product which can be stored, shipped and used safely without any of the problems associated with SAH slurries or solutions.